The invention relates to printers, and more particularly to a printer capable of arbitrarily changing the mounting position and number of tractor units.
Printers using a long sheet, i.e., a continuous web, include one in which a push-type pin tractor is disposed at the rear of the print position, as disclosed in Japanese Patent Unexamined Publication No. 71453/86, and one in which the push-type pin tractor is disposed in front of the print position, as proposed in Japanese Patent Unexamined Publication No. 163084/1989.
The former type of printer has the advantages that the web does not pass through the front of the printer, the printer can be installed on a Computer body or monitor, and the web can be located at the rear of the computer or on the floor, making it suitable for use in small space. However, its disadvantage is that replacement of the paper web is not easy. On the other hand, the latter type printer has the advantage that the web can be replaced from the front of the printer, but it also has the disadvantage that the location of the printer or web is limited because the web passes through the printer in the front, thereby making it unsuitable for use in a small space.
To solve the above problems, a printer such as disclosed in Japanese Patent Unexamined Publication No. 8070/1989 has two push-type pin tractors in front and at the rear of the print position. In this type of printer, however, the pin tractors cannot be detached, even though they may not be used depending on printing requirements. Thus, the printer is too expensive for some applications.